Barack Obama won the Nobel Peace Prize in 2009 for his extraordinary efforts to strengthen international diplomacy and cooperation between peoples. The Norwegian Nobel Committee emphasized his vision and work toward a world free from nuclear weapons, his promotion of multilateral diplomacy particularly through the United Nations, and his preference for dialogue and negotiations to resolve international conflicts. They also recognized his efforts to create a new climate in international politics that encouraged disarmament, arms control, and constructive responses to global challenges like climate change. His appeal for a global response to global challenges and his support for democracy and human rights were also key reasons for the award.

Specifically, Obama's efforts included promoting nuclear nonproliferation, fostering a new relationship between the Muslim world and the West, initiating plans to withdraw U.S. occupying forces from Iraq, and advocating for climate change measures. His 2009 speech in Cairo, which emphasized mutual respect and cooperation, was particularly influential in shaping international diplomacy.

Thus, the prize recognized both achievements already made and the hope he inspired for peaceful international relations and a better future.